Mathematical modelling of 4-chlorophenol inhibition on COD and 4-chlorophenol removals in an activated sludge unit

摘要

A mathematical model was developed for an activated sludge unit treating 4-chlorophenol (4-CP) containing synthetic wastewater composed of diluted molasses, urea, KH_2PO_4 and MgSO_4 with COD and 4-CP contents of 2500 and 500 mg l~(-1), respectively. The model included 4-CP inhibition on COD and 4-CP removals. Experimental data obtained at different hydraulic residence times (HRT = 5-30 h) and sludge ages (SRT, 3-30 days) were used to estimate the kinetic and inhibition constants for COD and 4-CP removal rates. 4-CP inhibition on COD removal was negligible while the inhibition on 4-CP removal was significant. The specific rate constant (k), saturation constant (K_s) for COD oxidation were found to be 2.64 day~(-1) and 559 mg l~(-1), respectively. A similar model was used for 4-CP oxidation in the activated sludge unit and the constants were found to be K = 1.44 day~(-1), K'_s = 25.7 mg l~(-1), K'_(CP) = 559 mg l~(-1) and K_(I,CP) = 17 mg l~(-1). Increases in death rate constant because of 4-CP inhibition was also quantified and the inhibition constants were determined for both COD and 4-CP removals. Model predictions with the estimated kinetic constants were in good agreement with the experimental data. Developed model can be used to estimate the performance of an activated sludge unit treating 4-CP containing wastewater under the specified experimental conditions.